1. Field of the Invention
The present invention relates to a treatment system and a treatment method employing a spiral wound type membrane module.
2. Description of the Background Art
A reverse osmosis membrane (RO membrane) separation device is employed for desalinating seawater, producing ultrapure water or the like. Coagulation precipitation sand filtration is mainly performed as pretreatment for the reverse osmosis membrane separation device. In such coagulation precipitation sand filtration, the quality of treated water varies with the quality of raw water, and hence treated water having stable quality cannot be supplied to the reverse osmosis membrane separation device. Thus, the ability of the reverse osmosis membrane separation device is limited.
The membrane separation technique is recently applied as pretreatment for the reverse osmosis membrane separation device. A hollow fiber membrane element is mainly employed for such pretreatment.
FIG. 18 illustrates an exemplary conventional treatment system employing a reverse osmosis membrane separation device 406.
Referring to FIG. 18, a reservoir 401 stores raw water such as river water. The raw water is supplied from the reservoir 401 to a supply pump 402 through a pipe 407, and further supplied to a hollow fiber membrane element 403 by the supply pump 402. The hollow fiber membrane element 403 separates the raw water into permeate and concentrate. The permeate obtained by the hollow fiber membrane element 403 is supplied to a reservoir 404 through a pipe 408 as pretreated water. The concentrate obtained by the hollow fiber membrane element 403 is returned to the reservoir 401 through a pipe 409.
The pretreated water stored in the reservoir 404 is supplied to a pump 405 through a pipe 410, and further supplied to the reverse osmosis membrane separation device 406 by the pump 405. The reverse osmosis membrane separation device 406 separates the pretreated water into permeate and concentrate. The permeate obtained by the reverse osmosis membrane separation device 406 is taken out through a pipe 411. The concentrate obtained by the reverse osmosis membrane separation device 406 is returned to the reservoir 401 through a pipe 412.
In the aforementioned conventional treatment system, the pretreated water obtained by the hollow fiber membrane element 403 must be temporarily stored in the reservoir 404, and the pretreated water must be supplied to the reverse osmosis membrane separation device 406 from the reservoir 404 by the pump 405. Thus, the system cost as well as the size of the system are increased due to the necessity for the reservoir 404 and the pump 405.
The hollow fiber membrane element 403 can attain a large membrane area (volumetric efficiency) per unit volume, but the membrane is disadvantageously easy to break. If the membrane of the hollow fiber membrane element 403 is broken, the quality of the pretreated water supplied to the reverse osmosis membrane separation device 406 is disadvantageously reduced.
An object of the present invention is to provide a treatment system, which can be reduced in cost and miniaturized, having high reliability.
A treatment system according to an aspect of the present invention comprises a spiral wound type membrane module including a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, one or a plurality of reverse osmosis membrane separation devices, provided on a succeeding stage of the spiral wound type membrane module, including reverse osmosis membranes, and a first duct, the spiral wound type membrane element includes a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component, and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, the raw liquid passage forming member is arranged to supply a raw liquid, supplied into the pressure vessel through the raw liquid inlet, into the perforated hollow pipe from at least the outer peripheral side of the spiral wound type membrane element, and the first duct is provided to supply a permeated liquid taken out from at least one opening end of the perforated hollow pipe to the one or a plurality of reverse osmosis membrane separation devices.
In the treatment system, the raw liquid is supplied to the spiral wound type membrane module, and the permeated liquid taken out from the spiral wound type membrane module is supplied to the reverse osmosis membrane separation device.
In this case, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel, for performing dead end filtration. Contaminants contained in the raw liquid are captured on at least the outer peripheral portion of the spiral wound type membrane element. The contaminants captured on the outer peripheral portion are readily removed in back wash reverse filtration.
As described above, dead end filtration is performed in the spiral wound type membrane element, whereby a pump for supplying the raw liquid to the spiral wound type membrane module may not have a large size. Further, the permeated liquid taken out from the spiral wound type membrane module can be directly fed to the reverse osmosis membrane separation device with pressure by the pump.
In this case, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure, and high pressure resistance is attained. Thus, the raw liquid can be supplied with high pressure by the pump for supplying the raw liquid to the spiral wound type membrane module.
In the aforementioned treatment system, neither a pump nor a reservoir is required for supplying the permeated liquid taken out from the spiral wound type membrane module to the reverse osmosis membrane separation device, whereby the system cost is reduced and the system is miniaturized.
In pretreatment with the spiral wound type membrane module, the quality of the permeated liquid is not varied with the quality of the raw liquid dissimilarly to the coagulation precipitation.sand filtration method. Therefore, a pretreated liquid having stable quality can be regularly supplied to the reverse osmosis membrane separation device, not to reduce the ability of the reverse osmosis membrane separation device.
No dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of the fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane for separating a fluid containing organic matter, therefore, high reliability is attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of the organic matter, decomposition of separation membranes and the like.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced.
In the treatment system, the one or a plurality of reverse osmosis membrane separation devices may include a plurality of serially connected reverse osmosis membrane separation devices, the first duct may be provided to supply the permeated liquid to a preceding stage reverse osmosis membrane separation device among the plurality of serially connected reverse osmosis membrane separation devices, and the treatment system may further comprise a second duct supplying the permeated liquid from the preceding stage reverse osmosis membrane separation device to a succeeding stage reverse osmosis membrane separation device, and a third duct returning a concentrated liquid from the succeeding stage reverse osmosis membrane separation device to the supply side of the preceding stage reverse osmosis membrane separation device.
In this case, the succeeding stage reverse osmosis membrane separation device further separates the permeated liquid from the preceding stage reverse osmosis membrane separation device into a concentrated liquid and a permeated liquid. The concentrated liquid from the succeeding stage reverse osmosis membrane separation device is supplied to the supply side of the preceding stage reverse osmosis membrane separation device again. Thus, a permeated liquid having high quality can be obtained with high recovery.
The treatment system may further comprise an ion exchanger provided on a succeeding stage of the one or a plurality of reverse osmosis membrane separation devices for treating the permeated liquid from the one or a plurality of reverse osmosis membrane separation devices.
In this case, the ion exchanger further treats the permeated liquid from the reverse osmosis membrane separation device, whereby a permeated liquid (pure water) having higher quality is obtained.
The treatment system may further comprise one or a plurality of pretreaters provided on a preceding stage of the spiral wound type membrane module for performing prescribed pretreatment on the raw liquid supplied to the spiral wound type membrane module.
In this case, a liquid pretreated by the pretreater is supplied to the spiral wound type membrane module as the raw liquid, whereby a load on the spiral wound type membrane element is reduced. Thus, the spiral wound type membrane module can be stably run with high reliability over a long period, whereby a treatment system enabling more stable running with higher reliability is implemented.
Particularly in the treatment system, the pretreater may include at least one of a sand filtration treater, activated sludge process equipment, a microfiltration membrane separation device, a centrifugal separator, a dipped membrane separation device, a pressure floatation treater, a coagulator, precipitation equipment, an ozone treater, a strong acid water treater, an ultraviolet bactericidal treater and a sodium hypochlorite bactericidal treater. Such a pretreater supplies a pretreated liquid from which contaminants are removed or a sterilized pretreated liquid to the spiral wound type membrane module.
A treatment system according to another aspect of the present invention comprises one or a plurality of pretreaters performing prescribed pretreatment, a spiral wound type membrane module, provided on a succeeding stage of the pretreaters, including a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, and a duct, the spiral wound type membrane element includes a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component, and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, the duct is provided to supply a treated liquid discharged from the one or a plurality of pretreaters into the pressure vessel through the raw liquid inlet, and the raw liquid passage forming member is arranged to supply the treated liquid, supplied into the pressure vessel, into the perforated hollow pipe from at least the outer peripheral side of the spiral wound type membrane element.
In the treatment system, the treated liquid pretreated by the pretreater is supplied to the spiral wound type membrane module, whereby a load on the spiral wound type membrane element is reduced. Thus, the spiral wound type membrane module can be stably run with high reliability over a long period.
In this case, the treated liquid discharged from the pretreater is supplied from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel for performing dead end filtration. Contaminants contained in the treated liquid discharged from the pretreater are captured on at least the outer peripheral portion of the spiral wound type membrane element. The contaminants captured on the outer peripheral portion are readily removed in back wash reverse filtration.
No dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of the fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane element for separating a fluid containing organic matter, therefore, high reliability is attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of the organic matter, decomposition of separation membranes and the like.
Further, the treated liquid discharged from the pretreater is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the treated liquid from the pretreater due to dead end filtration. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the treated liquid from the pretreater is supplied under high pressure. Thus, high pressure resistance is attained.
Particularly in the treatment system, the pretreater may include at least one of a sand filtration treater, activated sludge process equipment, a microfiltration membrane separation device, a centrifugal separator, a dipped membrane separation device, a pressure floatation treater, a coagulator, precipitation equipment, an ozone treater, a strong acid water treater, an ultraviolet bactericidal treater and a sodium hypochlorite bactericidal treater. Such a pretreater supplies a pretreated liquid from which contaminants are removed or a sterilized pretreated liquid to the spiral wound type membrane module.
A treatment system according to still another aspect of the present invention comprises one or a plurality of pretreaters performing prescribed pretreatment and supplying a treated liquid to a prescribed succeeding stage system, a spiral wound type membrane module including a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, and a duct, the spiral wound type membrane element includes a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component, and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, the duct is provided to supply a washing liquid, discharged from the one or a plurality of pretreaters in back wash reverse filtration of the one or a plurality of pretreaters, into the pressure vessel through the raw liquid inlet, and the raw liquid passage forming member is arranged to supply the washing liquid, supplied into the pressure vessel, into the perforated hollow pipe from at least the outer peripheral side of the spiral wound type membrane element.
In the treatment system, the washing liquid discharged from the pretreater in back wash reverse filtration is supplied to the spiral wound type membrane module. Thus, the spiral wound type membrane module removes contaminants contained in the washing liquid discharged from the pretreater, whereby the discharged washing liquid can be effectively utilized. In this case, the washing liquid discharged from the pretreater is supplied from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel for performing dead end filtration. Contaminants contained in the discharged washing liquid are captured on at least the outer peripheral portion of the spiral wound type membrane element. The contaminants captured on the outer peripheral portion are readily discharged in back wash reverse filtration.
In the aforementioned spiral wound type membrane module, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of the fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane element for separating a fluid containing organic matter, therefore, high reliability is attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of the organic matter, decomposition of separation membranes and the like.
Further, pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, the spiral wound type membrane module attains high recovery without employing a large pump for supplying the washing liquid discharged from the pretreater due to dead end filtration. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the discharged washing liquid is supplied under high pressure. Thus, high pressure resistance is attained.
In the treatment system, the pretreater may include a sand filtration treater or an activated carbon treater.
In the treatment system according to the present invention, the pressure vessel of the spiral wound type membrane module may further have a raw liquid outlet so that part of the treated liquid is regularly or intermittently taken out from the pressure vessel through the raw liquid outlet. Further, at least part of the taken-out treated liquid may be returned to the supply side of the spiral wound type membrane module again. In this case, a flow of the treated liquid can be formed axially along the outer peripheral portion of the spiral wound type membrane element by taking out part of the treated liquid. Thus, contaminants contained in the treated liquid can be inhibited from adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element, and part of the contaminants can be discharged with the treated liquid. In addition, the treated liquid (permeated liquid) is obtained with high recovery in the spiral wound type membrane module by returning at least part of the taken-out treated liquid to the supply side again.
A treatment method according to a further aspect of the present invention employs a treatment system comprising a spiral wound type membrane module including a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel and one or a plurality of reverse osmosis membrane separation devices, provided on a succeeding stage of the spiral wound type membrane module, including a reverse osmosis membrane, the spiral wound type membrane element includes a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component, and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises steps of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the spiral wound type membrane module and taking out a permeated liquid from at least one opening end of the perforated hollow pipe, and supplying the taken-out permeated liquid to the one or a plurality of reverse osmosis membrane separation devices.
In this case, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel for performing dead end filtration. Contaminants contained in the raw liquid are captured on at least the outer peripheral portion of the spiral wound type membrane element. The contaminants captured on the outer peripheral portion are readily removed in back wash reverse filtration.
As described above, dead end filtration is performed in the spiral wound type membrane module, whereby a pump for supplying the raw liquid to the spiral wound type membrane module may not have a large size. Further, the permeated liquid taken out from the spiral wound type membrane module can be directly fed to the reverse osmosis membrane separation device with pressure by the pump.
In this case, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure, and high pressure resistance is attained. Thus, the raw liquid can be supplied with high pressure by the pump for supplying the raw liquid to the spiral wound type membrane module.
In the aforementioned treatment system, neither a pump nor a reservoir is required for supplying the permeated liquid taken out from the spiral wound type membrane module to the reverse osmosis membrane separation device, whereby the system cost is reduced and the system is miniaturized.
In pretreatment with the spiral wound type membrane module, the quality of the permeated liquid is not varied with the quality of the raw liquid dissimilarly to the coagulation precipitation.sand filtration method. Therefore, a pretreated liquid having stable quality can be regularly supplied to the reverse osmosis membrane separation device, not to reduce the ability of the reverse osmosis membrane separation device.
No dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of the fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane element for separating a fluid containing organic matter, therefore, high reliability is attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of the organic matter, decomposition of separation membranes and the like.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced.
In the treatment method, the one or a plurality of reverse osmosis membrane separation devices may include a plurality of serially connected reverse osmosis membrane separation devices, and the treatment method may further comprise steps of supplying the permeated liquid from a preceding stage reverse osmosis membrane separation device to a succeeding stage reverse osmosis membrane separation device among the plurality of serially connected reverse osmosis membrane separation devices, and returning a concentrated liquid from the succeeding stage reverse osmosis membrane separation device to the supply side of the preceding stage reverse osmosis membrane separation device.
In this case, the succeeding stage reverse osmosis membrane separation device further separates the permeated liquid from the preceding stage reverse osmosis membrane separation device into a concentrated liquid and a permeated liquid. The concentrated liquid from the succeeding stage reverse osmosis membrane separation device is returned to the supply side of the preceding stage reverse osmosis membrane separation device again. Thus, a permeated liquid having high quality can be obtained with high recovery.
In the treatment method, the treatment system may further comprise an ion exchanger provided on a succeeding stage of the one or a plurality of reverse osmosis membrane separation devices, and the treatment method may further comprise a step of supplying the permeated liquid from the one or a plurality of reverse osmosis membrane separation devices to the ion exchanger.
In this case, the ion exchanger further treats the permeated liquid from the reverse osmosis membrane separation device, whereby a permeated liquid (pure water) having higher quality can be obtained.
In the treatment method, the treatment system may further comprise one or a plurality of pretreaters provided on a preceding stage of the spiral wound type membrane module, the treatment method may further comprise a step of performing prescribed pretreatment with the one or a plurality of pretreaters, and the step of supplying a raw liquid may include a step of supplying a treated liquid discharged from the pretreater to the spiral wound type membrane module as the raw liquid.
In this case, the treated liquid pretreated by the pretreater is supplied to the spiral wound type membrane module, whereby a load on the spiral wound type membrane element is reduced. Thus, the spiral wound type membrane module can be stably run with high reliability over a long period, whereby a treatment system enabling stable running with high reliability is implemented.
Particularly in the treatment method, the step of performing pretreatment may include a step of performing at least one of treatment with a sand filtration treater, treatment with activated sludge process equipment, treatment with a microfiltration membrane separation device, treatment with a centrifugal separator, treatment with a dipped membrane separation device, treatment with a pressure floatation treater, treatment with a coagulator, treatment with precipitation equipment, treatment with an ozone treater, treatment with a strong acid water treater, treatment with an ultraviolet bactericidal treater and treatment with a sodium hypochlorite bactericidal treater.
Such a pretreater can supply a treated liquid from which contaminants are removed or a sterilized treated liquid to the spiral wound type membrane module.
In the treatment method, the step of supplying a raw liquid may include a step of continuously or intermittently feeding a partial raw liquid axially along the outer peripheral portion of the spiral wound type membrane element and taking out the partial raw liquid from the pressure vessel. Thus, contaminants contained in the raw liquid can be inhibited from adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element, and part of the contaminants can be discharged with the raw liquid. At least part of the taken-out raw liquid may be returned to the supply side of the spiral wound type membrane module again. Thus, the permeated liquid can be obtained with high recovery in the spiral wound type membrane module.
A treatment method according to a further aspect of the present invention employs a treatment system comprising one or a plurality of pretreaters and a spiral wound type membrane module, provided on a succeeding stage of the one or a plurality of pretreaters, including a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element includes a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component, and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the treatment method comprises steps of performing prescribed pretreatment with the pretreater, and supplying a treated liquid, discharged from the pretreater, from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the spiral wound type membrane module and taking out a permeated liquid from at least one opening end of the perforated hollow pipe.
In the treatment method, the treated liquid pretreated by the pretreater is supplied to the spiral wound type membrane module, whereby a load on the spiral wound type membrane element is reduced. Thus, the spiral wound type membrane module can be stably run with high reliability over a long period.
In this case, the treated liquid discharged from the pretreater is supplied from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel, for performing dead end filtration. Contaminants contained in the treated liquid discharged from the pretreater are captured on at least the outer peripheral portion of the spiral wound type membrane element. The contaminants captured on the outer peripheral portion are readily removed in back wash reverse filtration.
No dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of the fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane element for separating a fluid containing organic matter, therefore, high reliability is attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of the organic matter, decomposition of separation membranes and the like.
Further, the treated liquid discharged from the pretreater is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the treated liquid due to dead end filtration. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the treated liquid from the pretreater is supplied under high pressure. Thus, high pressure resistance is attained.
Particularly in the treatment method, the step of performing pretreatment may include a step of performing at least one of treatment with a sand filtration treater, treatment with activated sludge process equipment, treatment with a microfiltration membrane separation device, treatment with a centrifugal separator, treatment with a dipped membrane separation device, treatment with a pressure floatation treater, treatment with a coagulator, treatment with precipitation equipment, treatment with an ozone treater, treatment with a strong acid water treater, treatment with an ultraviolet bactericidal treater and treatment with a sodium hypochlorite bactericidal treater.
Such a pretreater can supply a treated liquid from which contaminants are removed or a sterilized treated liquid to the spiral wound type membrane module.
In the treatment method, the step of supplying a treated liquid may include a step of continuously or intermittently feeding a partial treated liquid axially along the outer peripheral portion of the spiral wound type membrane element and taking out the partial treated liquid from the pressure vessel. Thus, contaminants contained in the treated liquid can be inhibited from adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element, and part of the contaminants can be discharged with the treated liquid. Further, at least part of the taken-out treated liquid may be returned to the supply side of the spiral wound type membrane module again. Thus, the permeated liquid is obtained with high recovery in the spiral wound type membrane module.
A treatment method according to a further aspect of the present invention employs a treatment system comprising one or a plurality of pretreaters performing prescribed pretreatment and supplying a treated liquid to a prescribed succeeding stage system, and a spiral wound type membrane module including a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element includes a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component, and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the treatment method comprises steps of performing back wash reverse filtration of the one or a plurality of pretreaters, and supplying a washing liquid, discharged from the one or a plurality of pretreaters in back wash reverse filtration, from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the spiral wound type membrane module and taking out a permeated liquid from at least one opening end of the perforated hollow pipe.
In the treatment method, the washing liquid discharged from the pretreater in back wash reverse filtration is supplied to the spiral wound type membrane module for removing contaminants with the spiral wound type membrane module. Thus, the washing liquid discharged from the pretreater can be effectively utilized.
In this case, the washing liquid discharged from the pretreater is supplied from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel for performing dead end filtration. Contaminants contained in the discharged washing liquid are captured on at least the outer peripheral portion of the spiral wound type membrane element. The contaminants captured on the outer peripheral portion are readily discharged in back wash reverse filtration.
In the aforementioned spiral wound type membrane module, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of the fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane element for separating a fluid containing organic matter, therefore, high reliability is attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of the organic matter, decomposition of separation membranes and the like.
Further, pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained in the spiral wound type membrane module without employing a large pump for supplying the washing liquid discharged from the pretreater due to dead end filtration. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the discharged washing liquid is supplied under high pressure. Thus, high pressure resistance is attained.
In the treatment method, the pretreater may include a sand filtration treater or an activated carbon treater.
In the treatment method, the step of supplying a washing liquid may include a step of continuously or intermittently feeding a partial washing liquid axially along the outer peripheral portion of the spiral wound type membrane element and taking out the partial washing liquid from the pressure vessel. Thus, contaminants contained in the washing liquid can be inhibited from adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element, and part of the contaminants can be discharged with the washing liquid. Further, at least part of the taken-out washing liquid may be returned to the supply side of the spiral wound type membrane module again. Thus, the permeated liquid is obtained with high recovery in the spiral wound type membrane module.
These and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.